Photophysics and Photocatalysis of Luminescent Transition Metal Carbene and Isocyanide Complexes

Inspired by the excellent emission properties of our recently developed isocyano Re(I) diimine complexes, [Re(CNR)₄(N–N)]⁺, [Re(CO)(CNR)₃(N–N)]⁺, and [Re(CO)₂(CNR)₂(N–N)]⁺, we have developed a new series of charge-neutral strongly phosphorescent isocyanoborato complexes for the electroluminescent device application. As these complexes display two different types of MLCT transitions {[dπ(Re) → π*(N–N)] and [dπ(Re) → π*(CNR)]}, we have also developed a new class of phosphorescent Re(I) isocyanide complexes. Although many of these isocyano complexes can be used as photocatalysts or photosensitizers, their applications are limited by the instability of the isocyanide ligands toward nucleophilic attack. In this context, we have extended our work to develop new classes of luminescent metal carbene (NHC) complexes. Some of these carbene complexes not only display interesting photophysical properties, they also exhibit excellent photocatalytic activity as well as CO₂ capturing properties. To elucidate the electronic structures of these complexes, DFT and TD-DFT calculations have also been performed.
On the other hand, the photoredox catalysis for organic transformations using the ³MLCT excited states of these complexes and the triplet emissive excited state of the cyclometalated Ir(III) complex, [Ir(ppy)₃]⁺ will also be reported.